DataNucleus supports persisting objects to RDBMS datastores (using the
datanucleus-rdbms plugin).
It supports the vast majority of RDBMS products available today.
DataNucleus communicates with the RDBMS datastore using JDBC. RDBMS systems accept varying standards
of SQL and so DataNucleus will support particular RDBMS/JDBC combinations only, though clearly we try
to support as many as possible.

By default when you create a PersistenceManagerFactory (PMF) to
connect to a particular datastore DataNucleus will automatically detect the
datastore adapter
to use and will use its own internal adapter for that type of datastore. If you find that either
DataNucleus has incorrectly detected the adapter to use, or that there is some issue with the
internal adapter, you can override the default behaviour. Please refer to the
Database Adapter Extension Guide for details.

The table below shows the versions of RDBMS and JDBC driver that DataNucleus has been tested with

If you have success with any other combinations for the above RDBMS or indeed with any other
RDBMS, please let us know so we can update our compatibility guide. We only show here what we
have either tried ourselves or what has been reported as successful.

MySQL is supported as an RDBMS datastore by DataNucleus with the following provisos

INNODB
tables must be used since it is the only table type that allows foreign keys etc at
the moment. You can however define what type your table uses by setting the <class>
extension "mysql-engine-type" to be MyISAM or whatever for the class being persisted.

JDOQL.isEmpty()/contains() will not work in MySQL 4.0 (or earlier) since the query uses EXISTS
and that is only available from MySQL 4.1

MySQL on Windows MUST specify
datanucleus.identifier.case
as "LowerCase" since the MySQL server
stores all identifiers in lowercase BUT the mysql-connector-java JDBC driver has a bug (in versions
up to and including 3.1.10) where it claims that the MySQL server stores things in mixed case when
it doesnt

MySQL 3.* will not work reliably with inheritance cases since DataNucleus requires UNION and this doesn't
exist in MySQL 3.*

MySQL before version 4.1 will not work correctly on JDOQL Collection.size(), Map.size() operations
since this requires subqueries, which are not supported before MySQL 4.1.

If you receive an error "Incorrect arguments to mysql_stmt_execute" then this is a bug in MySQL and
you need to update your JDBC URL to append "?useServerPrepStmts=false".

MySQL throws away the milliseconds on a Date and so cannot be used reliably for Optimistic locking
using strategy "date-time" (use "version" instead)

You can specify "BLOB", "CLOB" JDBC types when using MySQL with DataNucleus but you must turn validation
of columns OFF. This is because these types are not supported by the MySQL JDBC driver and
it returns them as LONGVARBINARY/LONGVARCHAR when querying the column type

To specify MySQL as your datastore, you will need something like the following specifying (replacing 'db-name'
with name of your database etc)

To specify Oracle as your datastore, you will need something like the following specifying (replacing 'db-name' with
name of your database etc) ... you can also use 'oci' instead of 'thin' depending on your driver.

Note that some database logging options in Informix do not allow changing autoCommit dinamically. You need to rebuild the database
to support it. To rebuild the database refer to Informix documention, but as example,
run $INFORMIXDIR\bin\dbaccess and execute the command "CREATE DATABASE mydb WITH BUFFERED LOG".

INDEXOF
: Informix 11.x does not have a function to search a string in another string.
DataNucleus defines a user defined function, DATANUCLEUS_STRPOS, which is automatically created
on startup. The SQL for the UDF function is:

ASCII
: Derby 10.1 does not have a function to convert a char into ascii code. DataNucleus needs
such function to converts chars to int values when performing queries converting chars to ints.
DataNucleus defines a user defined function, DataNucleus_ASCII, which is automatically created on startup.
The SQL for the UDF function is:

Firebird is supported as an RDBMS datastore by DataNucleus with the proviso that

Auto-table creation is severely limited with Firebird. In Firebird, DDL statements are not
auto-committed and are executed at the end of a transaction, after any DML statements. This makes
"on the fly" table creation in the middle of a DML transaction not work. You must make sure that
"autoStartMechanism" is NOT set to "SchemaTable" since this will use DML. You must also make sure
that nobody else is connected to the database at the same time. Don't ask us why such
limitations are in a RDBMS, but then it was you that chose to use it ;-)

To specify Firebird as your datastore, you will need something like the following specifying
(replacing 'db-name' with filename of your database etc)